This application relates to a method of determining a thickness of an inner wall in a gas turbine engine component.
Gas turbine engines are known and, typically, include a fan delivering air into a compressor section where it is compressed and delivered downstream into a combustor section. The air is mixed with fuel and ignited in the combustor section and products of this combustion pass downstream over turbine rotors driving them to rotate. The turbine rotors typically carry blades. Rows of static vanes are placed intermediate rows of the blades. The blades and the vanes become quite hot due to the hot products of combustion.
Thus, it is known to provide cooling channels within the gas turbine engine components. The blades and the vanes typically include an airfoil receiving the cooling channels. Historically, there were relatively large central cooling channels. A wall thickness between an outer wall of the airfoil and the channel must be carefully maintained and designed.
It was known in the art to provide various inspection means for measuring a thickness between the outer wall and the cooling channels in manufactured airfoils to ensure that it meets the design specifications. One method of measuring the wall thickness was flash thermography.
Flash thermography is a known method of measuring thickness or looking for flaws within a body. Essentially, a flash of light energy is directed off a component to be inspected. This dramatically and quickly raises the temperature of the component. An infrared camera repeatedly captures images of the surface and can determine changes in the heat at the surface. Modern flash thermography systems are able to evaluate those changes on a pixel by pixel basis and, thus, can provide temperature change information over very precise areas on the surface of the component.
Those changes can be translated to a thickness in the component based upon the material of the component and utilizing algorithms well known in the art.
More recently, gas turbine engine components having airfoils have been provided with so-called cooling channels. The cooling circuits are precisely made to an exact width and have sometimes been placed between an outer wall and the relatively larger central cooling channels.
Flash thermography is not able to provide accurate measurements of the distance from an inner wall of the microcircuit to the enlarged central cooling channel.